The present invention relates to a pneumatic tire to be mounted on industrial vehicles such as a forklift truck, shovel truck, and straddle carrier which are used for cargo handling. More particularly, it relates to a radial or sermiradial tire for industrial vehicles which is characterized in that the carcass cord is high-modulus cord such as steel cord and is arranged parallel to or at an angle of by 10.degree. to 30.degree. with respect to the sectional direction of the tire, and the crown has a plurality of stiff belts.
The tire of this kind is required to have such fundamental performance as high traction power for quick starts, quick responsive braking force, stability at the time of cargo handling, and durability including wear resistance, puncture resistance, and heat resistance. The requirements are far more rigorous than those for truck and bus tires, not to mention passenger car tires. This is attributable to the difference of the conditions under which they are used.
Since the modern forklift truck has a high traction power, the tires mounted on it are used under severe conditions such as quick turns, quick starts, and quick braking which are repeated one after another. As compared with the general vehicle tires, the forklift truck tires are subjected far more often to torsional moment such a condition in which a large load is applied to the tires on one side of the vehicle due to a centrifugal force that arises when the vehicle makes a turn. Moreover, the forklift truck tires are subjected to a great lateral force when a reckless operator drives a forklift with the load lifted. In the case of forklift truck tire, the standard load for one tire is established rather high for the size of the tire. Under these unfavorable conditions, the rubber and cord constituting the tire lose their interfacial adhesive strength very soon.
To avoid the above-mentioned troubles, the limits for speed and loadage are established for the industrial vehicle tires, and heat resistant tires or specially designed tires are used where the operation conditions are bad. Once the tire is likely to be used under the conditions which are not expected at the time of design, it is broken due to interfacial separation of materials and cut through damage, or it causes the user to make a complain about the lack of lateral stability.